Because Mario is meant to be the most overall balanced character, and that pretty much everyone on dabessdi has fought multiple Marios, lets kick off the new forums with a MU thread.
So, to start, Mario vs Ganon.
Ganon has greater range than Mario, so he will abuse that. Spacing attacks in this MU is very important or Mario will turn Ganon into combo food. Mario can also control stage space with Fireballs so be sure to do that as projectiles hurt Ganon a lot. A stage without many platforms helps in this MU as it hurts Ganon's evasion game around them. You'll want to play it safe around Ganon, only combo when you know you can or you may eat a powerful aerial. Remember that Ganon can kill you in just a few good hits, but to compensate, once you get Ganon offstage, he is extremely susceptible to cape, ending him.
I'd say this MU is 55-45 Mario, simply because Mario offstage game and projectile, as well as combo ability, and the power to kill at decent percents via fsmash and fair.